High-efficiency power amplifier (PA) design is increasingly becoming an integral part of wireless communication systems. The cellular base station market is slowly transitioning to gallium-nitride (GaN) based RF products that are expected to be suitable for fifth generation (5G) communications. Improvement of final-stage PA performance characteristics such as gain, output power, linearity, and DC-RF conversion efficiency remains a focus for researchers now within the context of stringent massive multiple input multiple output (MIMO) 5G requirements.
In general, a GaN device lends itself to high efficiency by carefully optimizing gate and drain I-V (current-voltage) waveforms. A GaN PA design often presents second harmonic frequency (or “2f0”) short termination (or in other cases non-short termination) at the gate or drain node of a GaN device employed by the GaN PA. However, due to device extrinsic parasitics, such a manner of termination can create a bottleneck that inhibits achieving optimum PA performance. Also, process variation of device technologies can result in part-to-part variation, which can produce variability in terms of optimum harmonic terminations. Hence, for industrial applications it is desirable to enable tunability to exploit PA performance fully and maximize the yield in the production environment.
For at least these reasons, therefore, it would be advantageous if one or more improved circuits, systems, or methods, and particularly one or more improved PA circuits, PA systems, or PA methods, could be developed in which improvements relating to any one or more of the above concerns, or one or more other concerns, could be achieved.